Time domain reflectometry system and method of use

Abstract

A non-invasive Time Domain Reflectometry transmission line system and method for measuring one or more parameters of an electromagnetic Radio Frequency pulse transmitted, and reflected, along a transmission line, the parameters including at least one of; amplitude, propagation velocity and/or propagation time between defined predetermined instances. The system includes a transmission line structure including three or more elongated transmission elements each having two distal ends. Each element is capable of being selectively activated in at least two distinct pairs having distinct geometric configurations relative to each other to generate at least two distinct electric field potentials without physical displacement of the transmission line.

1. A non-invasive Time Domain Reflectometry (TDR) transmission line system for measuring one or more parameters of an electromagnetic Radio Frequency (RF) pulse transmitted, and reflected, along a transmission line, said parameters including at least one of; amplitude, propagation velocity and/or propagation time between defined predetermined instances, said system including:
 a transmission line structure including three or more elongated transmission elements, each having two distal ends, wherein any of the three or more transmission elements may be selectively activated to transmit said RF pulse; 
 a mounting assembly, mounting each said transmission element at a first said distal end to form a spatially-separated transmission element array with the other second distal end of each transmission element being spaced from said mounting assembly; 
 an RF source that transmits an RF pulse along said transmission line to activate a selected pair of said transmission elements to generate an electric field between the transmission elements of said pair; 
 characterized in that said transmission elements are capable of selective activation in at least two distinct pairs of elements forming different transmission lines, each pair having distinct geometric configurations relative to the at least one other pair, to generate at least two distinct electric field potentials without physical displacement of the transmission line structure. 
 
     
     
       2. A non-invasive TDR transmission line system as claimed in  claim 1 , further including a controller, capable of selectively activating a said pair of transmission elements. 
     
     
       3. A non-invasive TDR transmission line system as claimed in  claim 2 , wherein the transmission element array is configured with at least two non-identical physical separations between pairs of transmission elements. 
     
     
       4. A non-invasive TDR transmission line system as claimed in  claim 2 , wherein the transmission elements are parallel rods. 
     
     
       5. A non-invasive TDR transmission line system as claimed in  claim 2 , further including a calibration system including:
 one or more transmission stubs attached to said mounting assembly substantially parallel to said transmission elements, each stub capable of being selectively activated to transmit an RF pulse; 
 each stub having two distal ends, a first stub end positioned in lateral alignment with a first end of a said transmission element and the second stub end being positioned in lateral alignment with the interface between the mounting assembly and an active portion of that transmission element. 
 
     
     
       6. A non-invasive TDR transmission line system as claimed in  claim 2 , wherein each pair of transmission elements is spaced from another pair such that each pair of transmission elements lie in a different plane to that of another pair. 
     
     
       7. A non-invasive TDR transmission line system as claimed in  claim 1 , wherein the transmission line structure is configured with at least two non-identical physical separations between pairs of transmission elements. 
     
     
       8. A non-invasive TDR transmission line system as claimed in  claim 7 , wherein the transmission elements are parallel rods. 
     
     
       9. A non-invasive TDR transmission line system as claimed in  claim 7 , further including a calibration system including:
 one or more transmission stubs attached to said mounting assembly substantially parallel to said transmission elements, each stub capable of being selectively activated to transmit an RF pulse; 
 each stub having two distal ends, a first stub end positioned in lateral alignment with a first end of a said transmission element and the second stub end being positioned in lateral alignment with the interface between the mounting assembly and an active portion of that transmission element. 
 
     
     
       10. A non-invasive TDR transmission line system as claimed in  claim 1 , wherein the transmission elements are parallel rods. 
     
     
       11. A non-invasive TDR transmission line system as claimed in  claim 10 , where the separation of the parallel rods is variable. 
     
     
       12. A non-invasive TDR transmission line system as claimed in  claim 1 , further including a calibration system including:
 one or more transmission stubs attached to said mounting assembly substantially parallel to said transmission elements, each stub capable of being selectively activated to transmit an RF pulse; 
 each stub having two distal ends, a first stub end positioned in lateral alignment with a first end of a said transmission element and the second stub end being positioned in lateral alignment with the interface between the mounting assembly and an active portion of that transmission element. 
 
     
     
       13. A non-invasive TDR transmission line system as claimed in  claim 12 , wherein the transmission stubs are formed from a material with a substantially corresponding electrical conductivity and permittivity to the transmission elements. 
     
     
       14. A non-invasive TDR transmission line system as claimed in  claim 1 , wherein each pair of transmission elements is spaced from another pair such that each pair of transmission elements lie in a different plane to that of another pair. 
     
     
       15. A method of non-invasive measurement of electrical permittivity, ∈ n  of n target materials by determining one or more parameters of an electromagnetic RF pulse transmitted by a TDR transmission line system spatially displaced from said target material, said parameters including amplitude and at least one of: propagation velocity and/or propagation time between defined predetermined points of the transmission line, said system including:
 a transmission line structure, including three or more elongated transmission elements, each having two distal ends, wherein any of the three or more transmission elements may be selectively activated to transmit said RF pulse; 
 a mounting assembly, mounting each said transmission element at a first said distal end to form a spatially-separated transmission element array with the other second distal end of each transmission element being spaced from said mounting assembly; 
 an RF source that transmits an RF pulse along said transmission line to activate a selected pair of said transmission elements to generate an electric field between the transmission elements of said pair; 
 said method characterized by the steps of: 
 a) activating a first pair of said transmission elements to transmit a first RF pulse; 
 b) measuring at least one pair of said first RF pulse parameters; 
 c) activating a second pair of said transmission elements to transmit a second RF pulse; 
 d) measuring at least one pair of said second RF pulse parameters; 
 e) activating an n th  distinct pair of said transmission elements to transmit an n th  RF pulse; 
 f) measuring at least one pair of said n th  RF pulse parameters; 
 g) repeating steps a)-d) n times for n target materials; and 
 h) using the n pairs of measurements to calculate the electrical permittivity ∈ 1  to ∈ n  for n target materials. 
 
     
     
       16. The method as claimed in  claim 15 , including the step of determining the parameters of propagation time between defined predetermined points for a signal-amplitude vs. time graphical representation, wherein:
 a start and stop point respectively denoting the transmitted pulse's transition from an interface between a head of the transmission element to an active portion of the transmission element and reflection from the transmission element second end are defined by steps including: 
 i. identifying a first unambiguous amplitude minima proximal the pulse transition from said head to said active portion of the transmission element and a second minima proximal to the pulse reflection from the second end of said transmission element; 
 ii. determining a first and a second maximum gradient adjacent to each of said first and said second minima respectively; 
 iii. calculating for each said minima, an intersection point between a first tangent to the first said maximum gradient and a constant amplitude value extrapolation of the corresponding minima; 
 iv. translating said first tangent to the second maximum gradient; 
 v. determining intersection points between the translation of said first tangent to the second maximum gradient and a constant amplitude value extrapolation of the corresponding minima; 
 vi. defining said intersection points as said predetermined start and stop points for calculating the pulse propagation time. 
 
     
     
       17. The method as claimed in  claim 16 , wherein said first maximum gradient is the maximum gradient adjacent said second minima. 
     
     
       18. The method of  claim 16 , wherein substantially identical RF pulses are transmitted along each distinct pair of transmission elements. 
     
     
       19. The method of  claim 15 , wherein substantially identical RF pulses are transmitted along each distinct pair of transmission elements. 
     
     
       20. A method of non-invasive measurement of electrical permittivity of a target material using a Time Domain Reflectometry (TDR) transmission line system, the method comprising the step of:
 determining the propagation time of an electromagnetic RF pulse transmitted along a pair of transmission elements between defined predetermined points of the transmission line using a TDR transmission line system for measuring one or more parameters of an electromagnetic Radio Frequency (RF)pulse transmitted, and reflected, along a transmission line, said parameters including at least one of; amplitude, propagation velocity and/or propagation time between defined predetermined instances, said system including: 
 a transmission line structure including three or more elongated transmission elements, each having two distal ends, wherein any of the three or more transmission elements may be selectively activated to transmit said RF pulse; 
 a mounting assembly, mounting each said transmission element at a first said distal end to form a spatially-separated transmission element array with the other second distal end of each transmission element being spaced from said mounting assembly; 
 an RF source that transmits an RF pulse along said transmission line to activate a selected pair of said transmission elements to generate an electric field between the transmission elements of said pair; 
 characterized in that said transmission elements are capable of selective activation in at least two distinct pairs of elements forming different transmission lines, each pair having distinct geometric configurations relative to the at least one other pair, to generate at least two distinct electric field potentials without physical displacement of the transmission line structure.